1. Field of the Invention
The present invention relates to an improvement of a heat pump type air conditioner using a cooling source and a heat-radiating source of a heat gas engine such as an external combustion engine using a Stirling cycle or the like.
2. Description of Related Art
There has been hitherto known a separation type air conditioner having such a structure that an indoor heat exchanger and an outdoor heat exchanger of an air conditioner are linked to a cooling (endothermic) source and a heat-radiating source of a heat gas engine using a Stirling cycle (as disclosed in Japanese Post-examined Patent Application No. Hei-5-65777).
The stirling cycle is a regenerative heat cycle using a combination of change of four states, such as an isovolumeric (constant-volume) heating process, an isothermal (constant-temperature) expansion process, an isovolumeric cooling process and an isothermal compression process. The air conditioner using the Stirling cycle does not use any CFSs as refrigerant, and performs its air conditioning operation by using cold water and hot water which are cooled and heated through a cooling (heat absorption) process and a heat-radiation process, respectively. The cooling and heat-radiating processes are performed by pressure-increasing and pressure-reducing operations of helium gas which is completely harmless. Therefore, this type of air conditioners has been expected to be one of the next-generation which is harmless to the natural environment.
The separation type air conditioner as described above utilizes an external heating system of forcedly heating working gas with a high-temperature side heat exchanger to take out a low-temperature medium from a low-temperature side heat exchanger and an intermediate-temperature medium from an intermediate-temperature side heat exchanger and then use the low-temperature medium for cooling and the intermediate medium for heating. Specifically, in room-cooling operation, a close cycle connecting the low-temperature side heat exchanger and the indoor heat exchanger, and a close cycle connecting the intermediate-temperature side heat exchanger and the outdoor heat exchanger are respectively formed by switching change-over valves. Therefore, the heat of the low-temperature medium is radiated into a room (i.e., the heat of the room is absorbed to the low-temperature medium) by the indoor heat exchanger to cool the room, and the heat of the intermediate medium is discharged to the outside by the outdoor heat exchanger. On the other hand, in room-heating operation, a close cycle connecting the intermediate-temperature side heat exchanger and the indoor heat exchanger is formed by switching the change-over valves. Therefore, the heat of the intermediate medium is discharged into the room by the indoor heat exchanger to heat the room, and the heat of the low-temperature medium is discharged to the outside (i.e., the heat of the outside is absorbed to the low-temperature medium) by the outdoor heat exchanger.
As described above, the above-mentioned conventional air conditioner is equipped with only one outdoor heat exchanger and only one indoor heat exchanger. Accordingly, when the outdoor heat exchanger is frosted during the room-heating operation in the air conditioner thus constructed, only the following defrosting manner can be effectively used. That is, in the room-heating operation, the hot water (cold water) which is obtained through heat exchange operation based on heat-radiation action (cooling (heat absorption) action) in the Stirling cycle, flows into the indoor heat exchanger (the outdoor heat exchanger) during room-heating operation, whereby the room is heated. At this time, when the outdoor heat exchanger is frosted, the room-heating operation is temporarily stopped, and then the hot water which has been used to heat the room is made to flow into the frosted outdoor heat exchanger, thereby defrosting the frosted outdoor heat exchanger. However, the temporary cease operation of the room-heating operation reduces driving efficiency of the air conditioner. Further, in a middle season such as a rainy or wet season, the indoor heat exchanger is sometimes required to perform dry operation. In order to perform the dry operation, the cold water is made to flow in the indoor heat exchanger while the hot water is made to flow in the outdoor heat exchanger. At this time, the room is dried by the cold water, but at the same time it is cooled by the cold water. Accordingly, it is difficult to perform slightly heating or slightly cooling dry operation.